\section{Current practice}
\begin{frame}{Current practice}
\begin{center}
\begin{tikzpicture}
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\draw[thick,color=black,fill=white] (3,0) node{\nodeTwoName} circle (0.25);
\draw[thick,color=black,fill=white] (6,0) node{\nodeThreeName} circle (0.25);
\draw [very thick, ->] (0.5,0) -- (2.5,0) node[above=2mm, left=0.75cm]{A};
\end{tikzpicture}

\vspace{5mm}

\begin{tikzpicture}
\draw[thick,color=black,fill=white] (0,0) node{\nodeOneName} circle (0.25) node[left=4mm]{2$^{\mathrm{nd}}$};
\draw[thick,color=black,fill=white] (3,0) node{\nodeTwoName} circle (0.25);
\draw[thick,color=black,fill=white] (6,0) node{\nodeThreeName} circle (0.25);
\draw [very thick, <-] (3.5,0) -- (5.5,0) node[above=2mm, left=0.75cm]{B};
\end{tikzpicture}

\vspace{5mm}

\begin{tikzpicture}
\draw[thick,color=black,fill=white] (0,0) node{\nodeOneName} circle (0.25) node[left=4mm]{3$^{\mathrm{th}}$};
\draw[thick,color=black,fill=white] (3,0) node{\nodeTwoName} circle (0.25);
\draw[thick,color=black,fill=white] (6,0) node{\nodeThreeName} circle (0.25);
\draw [very thick, <-] (0.5,0) -- (2.5,0) node[above=2mm, left=0.75cm]{B};
\end{tikzpicture}

\vspace{5mm}

\begin{tikzpicture}
\draw[thick,color=black,fill=white] (0,0) node{\nodeOneName} circle (0.25) node[left=4mm]{4$^{\mathrm{th}}$};
\draw[thick,color=black,fill=white] (3,0) node{\nodeTwoName} circle (0.25);
\draw[thick,color=black,fill=white] (6,0) node{\nodeThreeName} circle (0.25);
\draw [very thick, ->] (3.5,0) -- (5.5,0) node[above=2mm, left=0.75cm]{A};
\end{tikzpicture}
\end{center}
\end{frame}